// This has the programs for computing the number of 1-bits
// in a word, or byte, etc.
// Max line length is 57, to fit in hacker.book.
#include <stdio.h>
#include <stdlib.h>     //To define "exit", req'd by XLC.

unsigned rotatel(unsigned x, int n) {
   if ((unsigned)n > 63) {printf("rotatel, n out of range.\n"); exit(1);}
   return (x << n) | (x >> (32 - n));
}

int pop0(unsigned x) {
   x = (x & 0x55555555) + ((x >> 1) & 0x55555555);
   x = (x & 0x33333333) + ((x >> 2) & 0x33333333);
   x = (x & 0x0F0F0F0F) + ((x >> 4) & 0x0F0F0F0F);
   x = (x & 0x00FF00FF) + ((x >> 8) & 0x00FF00FF);
   x = (x & 0x0000FFFF) + ((x >>16) & 0x0000FFFF);
   return x;
}

int pop1(unsigned x) {
   x = x - ((x >> 1) & 0x55555555);
   x = (x & 0x33333333) + ((x >> 2) & 0x33333333);
   x = (x + (x >> 4)) & 0x0F0F0F0F;
   x = x + (x >> 8);
   x = x + (x >> 16);
   return x & 0x0000003F;
}
/* Note: an alternative to the last three executable lines above is:
   return x*0x01010101 >> 24;
if your machine has a fast multiplier (suggested by Jari Kirma). */

int pop2(unsigned x) {
   unsigned n;

   n = (x >> 1) & 033333333333;       // Count bits in
   x = x - n;                         // each 3-bit
   n = (n >> 1) & 033333333333;       // field.
   x = x - n;
   x = (x + (x >> 3)) & 030707070707; // 6-bit sums.
   return x%63;                       // Add 6-bit sums.
}
/* An alternative to the "return" statement above is:
   return ((x * 0404040404) >> 26) +  // Add 6-bit sums.
           (x >> 30);
which runs faster on most machines (suggested by Norbert Juffa). */

int pop3(unsigned x) {
   unsigned n;

   n = (x >> 1) & 0x77777777;        // Count bits in
   x = x - n;                        // each 4-bit
   n = (n >> 1) & 0x77777777;        // field.
   x = x - n;
   n = (n >> 1) & 0x77777777;
   x = x - n;
   x = (x + (x >> 4)) & 0x0F0F0F0F;  // Get byte sums.
   x = x*0x01010101;                 // Add the bytes.
   return x >> 24;
}

int pop4(unsigned x) {
   int n;

   n = 0;
   while (x != 0) {
      n = n + 1;
      x = x & (x - 1);
   }
   return n;
}

int pop5(unsigned x) {
   int i, sum;

// Rotate and sum method        // Shift right & subtract

   sum = x;                     // sum = x;
   for (i = 1; i <= 31; i++) {  // while (x != 0) {
      x = rotatel(x, 1);        //    x = x >> 1;
      sum = sum + x;            //    sum = sum - x;
   }                            // }
   return -sum;                 // return sum;
}

int pop5a(unsigned x) {
   int sum;

                                // Shift right & subtract

                                   sum = x;
                                   while (x != 0) {
                                      x = x >> 1;
                                      sum = sum - x;
                                   }
                                   return sum;
}

int pop6(unsigned x) {               // Table lookup.
   static char table[256] = {
      0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4,
      1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
      1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
      2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,

      1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
      2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
      2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
      3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,

      1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
      2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
      2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
      3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,

      2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
      3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
      3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
      4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8};

   return table[x         & 0xFF] +
          table[(x >>  8) & 0xFF] +
          table[(x >> 16) & 0xFF] +
          table[(x >> 24)];
}

// The following works only for 8-bit quantities.
int pop7(unsigned x) {
   x = x*0x08040201;    // Make 4 copies.
   x = x >> 3;          // So next step hits proper bits.
   x = x & 0x11111111;  // Every 4th bit.
   x = x*0x11111111;    // Sum the digits (each 0 or 1).
   x = x >> 28;         // Position the result.
   return x;
}

// The following works only for 7-bit quantities.
int pop8(unsigned x) {
   x = x*0x02040810;    // Make 4 copies, left-adjusted.
   x = x & 0x11111111;  // Every 4th bit.
   x = x*0x11111111;    // Sum the digits (each 0 or 1).
   x = x >> 28;         // Position the result.
   return x;
}

// The following works only for 15-bit quantities.
int pop9(unsigned x) {
   unsigned long long y;
   y = x * 0x0002000400080010ULL;
   y = y & 0x1111111111111111ULL;
   y = y * 0x1111111111111111ULL;
   y = y >> 60;
   return y;
}

int errors;
void error(int x, int y) {
   errors = errors + 1;
   printf("Error for x = %08x, got %08x\n", x, y);
}

int main() {
   int i, n;
   static int test[] = {0,0, 1,1, 2,1, 3,2, 4,1, 5,2, 6,2, 7,3,
      8,1, 9,2, 10,2, 11,3, 12,2, 13,3, 14,3, 15,4, 16,1, 17,2,
      0x3F,6, 0x40,1, 0x41,2, 0x7f,7, 0x80,1, 0x81,2, 0xfe,7, 0xff,8,
      0x4000,1, 0x4001,2, 0x7000,3, 0x7fff,15,
      0x55555555,16, 0xAAAAAAAA, 16, 0xFF000000,8, 0xC0C0C0C0,8,
      0x0FFFFFF0,24, 0x80000000,1, 0xFFFFFFFF,32};

   n = sizeof(test)/4;

   printf("pop0:\n");
   for (i = 0; i < n; i += 2) {
      if (pop0(test[i]) != test[i+1]) error(test[i], pop0(test[i]));}

   printf("pop1:\n");
   for (i = 0; i < n; i += 2) {
      if (pop1(test[i]) != test[i+1]) error(test[i], pop1(test[i]));}

   printf("pop2:\n");
   for (i = 0; i < n; i += 2) {
      if (pop2(test[i]) != test[i+1]) error(test[i], pop2(test[i]));}

   printf("pop3:\n");
   for (i = 0; i < n; i += 2) {
      if (pop3(test[i]) != test[i+1]) error(test[i], pop3(test[i]));}

   printf("pop4:\n");
   for (i = 0; i < n; i += 2) {
      if (pop4(test[i]) != test[i+1]) error(test[i], pop4(test[i]));}

   printf("pop5:\n");
   for (i = 0; i < n; i += 2) {
      if (pop5(test[i]) != test[i+1]) error(test[i], pop5(test[i]));}

   printf("pop5a:\n");
   for (i = 0; i < n; i += 2) {
      if (pop5a(test[i]) != test[i+1]) error(test[i], pop5a(test[i]));}

   printf("pop6:\n");
   for (i = 0; i < n; i += 2) {
      if (pop6(test[i]) != test[i+1]) error(test[i], pop6(test[i]));}

   printf("pop7:\n");
   for (i = 0; i < n; i += 2) {
      if ((test[i] & 0xffffff00) == 0)
      if (pop7(test[i]) != test[i+1]) error(test[i], pop7(test[i]));}

   printf("pop8:\n");
   for (i = 0; i < n; i += 2) {
      if ((test[i] & 0xffffff80) == 0)
      if (pop8(test[i]) != test[i+1]) error(test[i], pop8(test[i]));}

   printf("pop9:\n");
   for (i = 0; i < n; i += 2) {
      if ((test[i] & 0xffff8000) == 0)
      if (pop9(test[i]) != test[i+1]) error(test[i], pop9(test[i]));}

   if (errors == 0)
      printf("Passed all %d cases.\n", sizeof(test)/8);
}
